Known methods for obtaining a zirconia sol include: a method for heat-hydrolyzing a zirconium salt aqueous solution, a method for adding hydrogen peroxide to a zirconium salt aqueous solution and heating the resultant solution, and a method for heating zirconium hydroxide in a basic region. For example, the following methods are disclosed.
There is proposed a method for hydrolyzing a reaction product between ammonium zirconium carbonate and a chelating agent (for example, oxyphenols, amino alcohols, oxyacids, polycarboxylic acids, oxyaldehydes, amino acids, and β-diketones) (See Patent Document 1).
Also, there is proposed a production method of a basic zirconia sol including: maintaining an aqueous dispersion containing zirconium hydroxide in a heated state at 80° C. or more until the crystallinity of produced zirconia becomes 80% or more to obtain an aqueous dispersion containing crystallized zirconia; and adding thereto, a basic compound containing nitrogen (primary amine, secondary amine, or quaternary ammonium hydroxide) or a hydroxide of an alkali metal or alkaline earth metal (See Patent Document 2).
Further, there is proposed a production method of a zirconia sol including: causing a precipitate by adding a basic substance to a zirconium salt aqueous solution; adding thereto, a hydroxide of an alkaline earth metal or an aqueous solution thereof to obtain a dispersion; and heat-aging the obtained dispersion at a temperature of 90 to 200° C. (See Patent Document 3).    [Patent Document 1] JP-A 3-174325 (1991) (Claims)    [Patent Document 2] JP-A 64-083519 (1989) (Claims)    [Patent Document 3] JP-A 60-176920 (1985) (Claims)